SCons will also search in repositories
for the SConstruct file and any specified SConscript files.
This poses a problem, though: how can SCons search a
repository tree for an SConstruct file
if the SConstruct file itself contains the information
about the pathname of the repository?
To solve this problem, SCons allows you
to specify repository directories
on the command line using the -Y option:

% scons -Q -Y /usr/repository1 -Y /usr/repository2

When looking for source or derived files,
SCons will first search the repositories
specified on the command line,
and then search the repositories
specified in the SConstruct or SConscript files.